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TI-2026-69573 Aliases CVE-2026-107585GHSA-ff4v-mg5q-r7g9

Resource exhaustion in hMailServer sign-in tables denies single sign-on

Priority LOW 30CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-770.

Summary

Uncontrolled eviction in the pending sign-in tables of the REST API in Progressive Robot hMailServer from 6.3.4 before 6.3.6 lets a remote unauthenticated attacker make other users' OpenID Connect, SAML and passkey sign-ins fail. The routes that start single sign-on and passkey challenges are reachable without authentication and store pending state in bounded tables that drop the oldest entry when full, so an attacker who keeps starting sign-ins pushes other users' pending sign-ins out before they return. Single sign-on and passkey sign-in are denied for as long as the requests continue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

Uncontrolled eviction in the pending sign-in tables of the REST API in Progressive Robot hMailServer 6.3.4 and 6.3.5 allows a remote unauthenticated attacker to make other users' OpenID Connect, SAML and passkey sign-ins fail. The routes that start a single sign-on and hand out a passkey sign-in challenge are reached without authentication and stored pending state in bounded tables that dropped their oldest entry when full, whoever had started it. An attacker who starts sign-ins a few times a second (about a hundred a second for passkeys) pushes every other user's pending sign-in out of the table before that user's browser returns, denying single sign-on and passkey sign-in for as long as the requests continue.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00448 39th percentileScored 2026-11-07
Fix Fixed hMailServer (Progressive Robot Ltd): 6.3.6

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Progressive Robot LtdhMailServer6.3.4 to before 6.3.66.3.6Patch availableCNA
  • hMailServer VendorProgressive Robot Ltd Affected 6.3.4 to before 6.3.6 Fixed in 6.3.6 Patch available CNA

Remediation

Upgrade hMailServer to version 6.3.6 or later, which fixes the flaw. The sources list no advisory identifier for this fix.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA hMailServer (Progressive Robot Ltd) Fixed in 6.3.6

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Progressive Robot hMailServer 6.3.6

    23 records Highest priority Priority LOW 23 LOW

    Other records, highest priority first

    • TI-2026-69567 Inefficient processing in hMailServer stalls mail deliveryPriority LOW 39
    • TI-2026-69565 Infinite loop in hMailServer MIME handling lets attackers stop mailPriority LOW 39
    • TI-2026-69564 Inefficient DKIM and ARC checks in hMailServer cause denial of servicePriority LOW 39
    Show all 23 records →

Timeline

  1. 2026-10-08 Threatist record created from CVE-2026-107585
  2. 2026-10-08 Alias added: GHSA-ff4v-mg5q-r7g9
  3. 2026-10-09 CISA SSVC decision points changed

References

Other 2

  • TI-2026-64884 Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in hMailServer CVSS 3.1CRITICAL 9.8
  • TI-2026-76418 Unchecked loop limit in hMailServer lets remote attackers stop mail CVSS 3.1HIGH 7.5
  • TI-2026-69567 Inefficient processing in hMailServer stalls mail delivery CVSS 3.1HIGH 7.5
  • TI-2026-69565 Infinite loop in hMailServer MIME handling lets attackers stop mail CVSS 3.1HIGH 7.5
  • TI-2026-69564 Inefficient DKIM and ARC checks in hMailServer cause denial of service CVSS 3.1HIGH 7.5
  • TI-2026-69562 Inefficient JSON parsing in hMailServer lets attackers halt mail CVSS 3.1HIGH 7.5
See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences